1. Field of the Invention
The present invention relates to ungelled reaction products prepared from polyoxyalkylenepolyamines and to the use of these reaction products for cationic electrodeposition.
2. Brief Description of the Prior Art
Electrodeposition as a coating application method involves the deposition of a film-forming composition under the influence of applied electrical potential. Electrodeposition has become increasingly important in the coatings industry because by comparison with non-electrophoretic coating means, electrodeposition offers higher paint utilizations, outstanding corrosion protection and low environmental contamination. Initially, electrodeposition was conducted with the workpiece being coated serving as the anode. This was familiarly referred to as anionic electrodeposition. However, in 1972, cationic electrodeposition was introduced commercially. Since that time, cationic electrodeposition has steadily gained in popularity and today is by far the most prevalent method of electrodeposition. Throughout the world more than 80 percent of all motor vehicles produced are given a primer coating by cationic electrodeposition. Other areas of application are primer coating or one-coat topcoating of automobile accessories, farm machinery, house and electrical appliances, steel furniture and structural components.
A serious problem associated with electrodeposition as practiced industrially is appearance defects in films. Such defects include film rupturing, the formation of pinholes and craters. The sources of film defects unfortunately are many and some of the more important sources are believed to be impurities or contaminants in the electrodeposition bath which may be, for example, oil or pretreatment chemicals introduced into the bath along with the article to be coated. One solution to the problem is to eliminate the impurities or source of contamination. However, this is not always practical on an industrial scale.
U.S. Pat. No. 4,423,166 describes an additive which can be added to a cationic electrodeposition bath to improve surface appearance of the electrodeposited coatings. The agent is the ungelled reaction product of a polyepoxide and a polyoxyalkylenepolyamine. Unfortunately, although being effective in improving surface appearance, the reaction product can cause adhesion problems of the electrodeposited coatings to subsequently applied materials such as sealer coats, top coats and adhesives.